The fields of clinical and analytical chemistry utilize many devices and apparatuses for studying analytes in samples. An entire subfield, referred to hereafter as "dry chemistry techniques" involves the production of devices which can be used to carry out sample analyses. These devices facilitate prompt and accurate measurement of particular substances. They are easy to use, thereby permitting patient self testing, "over the counter" use, and so forth.
A particularly useful form of a dry chemistry device is the test strip. While there are a vast number of test strips available, they can be described generally. In brief, a test strip involves a matrix which can receive a test sample. The matrix usually contains one or more reagents impregnated or somehow incorporated therein, which combine with the substance of interest (the "analyte") in a reaction or series of reactions leading to generation of some detectable signal, e.g., a color. The matrix is usually supported by some non-reactive material, such as a thermoplastic or cellulose base.
The matrix of these test devices must be made of a material which does not deteriously effect the reaction leading to the previously mentioned detectable signal. Further, it must be sturdy and stable. These qualities are important, because test strips are usually stored for at least a short period of time before use, and deterioration of the matrix would interfere with the use of the strip in analyte determination. To this end, the materials used to make the matrices are preferably polymers. Examples of polymers which are used in preparing such matrices may be found in, e.g., PCT Application PCT/US91/09819, assigned to the assignee of the subject application, as well as in U.S. Pat. Nos. 4,966,856 to Ito et al., 4,689,309 to Jones, and 4,868,106, to Ito et al. All of the foregoing references are incorporated by reference. Also incorporated by reference are U.S. Pat. Nos. 4,786,595 to Arai et al., U.S. Pat. No. 4,576,793 to Koyama et al., U.S. Pat. No. 4,427,632 to Okaniwa et al., U.S. Pat. No. 4,258,001 to Pierce et al., U.S. Pat. No. 4,147,76, to Levy et al., and U.S. Pat. No. 4,060,678 to Stickler. Some of the polymers disclosed in these references are summarized infra, and show the diverse types of polymers useful in test strip manufacture.
In preparing matrices of the type described herein, the reagents necessary for the diagnostic reaction are incorporated, preferably via a liquid medium with the matrix polymer. The resulting solution, suspension, emulsion, e.g., is then poured or otherwise dispensed so as to form a thin film. The film is treated so as to remove the liquids present therein, and the resulting film is rolled and stored. In order to prepare test strips using the matrix, appropriate lengths of film are unrolled and converted to the desired size.
A serious problem in this procedure is that many polymer films, even when dry, exhibit a residual tackiness, stickiness, or blocking which is not surprising when one considers that many of the polymers are also used as adhesives, floor polishes, and the like. When rolled, the coatings or films adhere to each other, and when unrolled, there is tearing or blocking and other deterioration caused because of the tackiness. As a result, there is a need for polymer materials treated so as to eliminate or to reduce tackiness and consequently to eliminate the problems discussed supra. Any approach taken to solving this problem, however, must also consider whether the materials incorporated into the film, i.e., the reagents useful for analyte determination are damaged via the treatment.
In PCT application PCT/US91/09819, non-aqueous polymer systems are described. These systems are used to prepare reagent films useful in determining analytes. This reference is silent, however, with respect to water based polymer systems, such as aqueous polymer emulsions and solutions. Compositions of this category are the subject of the present invention.
It has now been found, surprisingly, that polymer films of the type described herein can be made in a manner which alleviates the tackiness problem without interfering with the reagents included in the film.